Known dispensing apparatus commonly include a valve mechanism fitted to a container which is refilled with a product, for example mastic or sealant, which is to be dispensed. Examples are disclosed in Patent document EP-B-0243393 (Rocep Lusol Holdings Limited). However, known arrangements have several disadvantages.
For example, the cost of components used in the manufacture of such known apparatus is high. This is particularly true in relation to the cans used as containers in such apparatus. Further, automatic assembly of such apparatus is complicated and costly.
Yet another disadvantage is that the product must be filled into the dispensing apparatus during manufacture of the apparatus. This involves the product manufacturer supplying the product in bulk to the apparatus manufacturer who then returns the filled apparatus to the product manufacturer for sale. This is costly and inconvenient. As a result of the foregoing, the overall costs associated with presently available dispensing apparatus are high.
Known dispensing apparatus, such as that disclosed in EP-B-0089971 (Rocep Lusol Holdings Limited), include piston arrangements which are designed to prevent propellant gas in the apparatus from coming into contact with the product to be dispensed. Commonly, these piston arrangements consist of a pair of pistons with sealant therebetween. However, known arrangements can be costly to manufacture and have the significant disadvantage that after filling of the apparatus, and during storage, the sealant expands causing the pistons to separate from one another. This problem has to be addressed by "necking in" the can (ie locally reducing the diameter of the can) below the piston assembly to prevent separation. It would be desirable to have a piston arrangement which would stay together without the need for "necking in" the can.
It would also be desirable to have dispensing apparatus such that a manufacturer can fill the apparatus with product himself, after the apparatus has been assembled and/or pressurised, and to have dispensing apparatus which is refillable.